scholarly journals Towards Accurate Prediction of Unbalance Response, Oil Whirl and Oil Whip of Flexible Rotors Supported by Hydrodynamic Bearings

Lubricants ◽  
2016 ◽  
Vol 4 (3) ◽  
pp. 33 ◽  
Author(s):  
Rob Eling ◽  
Mathys te Wierik ◽  
Ron van Ostayen ◽  
Daniel Rixen
Keyword(s):  
Accurate Prediction ◽  
Hydrodynamic Bearings ◽  
Unbalance Response ◽  
Oil Whip ◽  
Flexible Rotors ◽  
Oil Whirl

Controlling Journal Bearing Instability Using Active Magnetic Bearings

2007 ◽  
Author(s):  
A. El-Shafei ◽  
A. S. Dimitri
Keyword(s):  
Journal Bearing ◽  
Magnetic Bearing ◽  
Journal Bearings ◽  
Active Magnetic Bearing ◽  
Rotating Speed ◽  
Damping Characteristics ◽  
Oil Whip ◽  
Novel Approach ◽  
Oil Whirl ◽  
Load Carrying

Journal Bearings are excellent bearings due to their large load carrying capacity and favorable damping characteristics. However, Journal bearings are known to be prone to instabilities. The oil whirl and oil whip instabilities limit the rotor maximum rotating speed. In this paper, a novel approach is used to control the Journal bearing (JB) instability. An Active Magnetic Bearing (AMB) is used to overcome the JB instability and to increase its range of operation. The concept is quite simple: rather than using the AMB as a load carrying element, the AMB is used as a controller only, resulting in a much smaller and more efficient AMB. The load carrying is done by the Journal bearings, exploiting their excellent load carrying capabilities, and the JB instability is overcome with the AMB. This results in a combined AMB/JB that exploits the advantages of each device, and eliminates the deficiencies of each bearing. Different controllers for the AMB to control the JB instability are examined and compared theoretically and numerically. The possibility of collocating the JB and the AMB is also examined. The results illustrate the effectiveness of the concept.

Analysis of Flexible Rotor Whirl and Whip Using a Realistic Hydrodynamic Journal Bearing Model

1976 ◽  
Vol 98 (4) ◽  
pp. 1135-1143 ◽  
Author(s):  
S. T. Myrick ◽  
H. G. Rylander
Keyword(s):  
Analytical Model ◽  
Reynolds Equation ◽  
Nonlinear Differential Equations ◽  
Flexible Rotor ◽  
State Response ◽  
Oil Whip ◽  
Flexible Rotors ◽  
Inlet Geometry ◽  
Hydrodynamic Journal Bearing ◽  
Transient And Steady State

An analytical method has been developed for the simulation of the transient and steady-state response of flexible rotors supported by realistic incompressible-film hydrodynamic journal bearings. The coupled nonlinear differential equations of rotor motion, formulated as an initial-value problem, are solved in conjunction with a “realistic” Reynolds equation solution which includes finite bearing length, wedge and squeeze films, fluid film cavitation, oil inlet geometry, and eccentricity and tilt (gyroscopics) of the journal. Presented in this paper are some of the results of a numerical and experimental study of rotor whirl using that analytical model. The response of a flexible rotor, for speeds up to the threshold of instability, is demonstrated as a function of disk unbalance and viscous damping. The validity of the analytical model is confirmed by comparison of experimental whirl data with numerical simulations of the response of the test rotor through the critical speed region to the onset of oil whip.

Sub-Synchronous Shaft Oscillations due to Oil Supply

2018 ◽  
Author(s):  
Luboš Smolík ◽  
Jan Rendl ◽  
Jan Stifter ◽  
Milan Omasta
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Computational Analysis ◽  
The Finite Element Method ◽  
Test Rig ◽  
Oil Supply ◽  
Oil Whip ◽  
Oil Whirl ◽  
Multi Body ◽  
Element Method

This paper aims at the modelling and investigation of unstable journal bearing with an emphasis on instabilities such as oil-whirl or further induced oil-whip. For this reason, a test rig for the investigation of these phenomena was built. Geometry, parameters and operating cases of the rig are described in detail in the presented paper. Computational analysis of the test rig was performed using two methods — the finite element method and a multi-body approach. The calculations of pressure distribution in journal bearings were also performed applying two methods — the finite difference method and the finite element method. The results of the analysis are properly introduced and discussed at the end of this paper. The results suggest that a yet unknown sub-synchronous component may appear under specific conditions. The component typically appears at frequency 0.9–0.98 of shaft speed and is likely caused by a location of a bore for oil supply.

Influence of Lubricant Film Cavitation On the Vibration Behaviour of a Semi-Floating Ring Supported Turbocharger Rotor with Thrust Bearing

2021 ◽  
Author(s):  
Christian Ziese ◽  
Cornelius Irmscher ◽  
Steffen Nitzschke ◽  
Christian Daniel ◽  
Elmar Woschke ◽  
...  
Keyword(s):  
Squeeze Film ◽  
Two Phase ◽  
Hydrodynamic Bearing ◽  
Lubricating Film ◽  
Oil Whip ◽  
Oil Whirl ◽  
Bearing Stiffness ◽  
Run Up ◽  
Stiffness And Damping ◽  
The Impact

Abstract This contribution investigates the influence of outgassing processes on the vibration behaviour of a hydrodynamic bearing supported turbocharger rotor. The examined rotor is supported radially by floating rings with outer squeeze-film damping and axially by thrust bearings. Due to the highly non-linear bearing properties, the rotor can be excited via the lubricating film, which results in sub-synchronous vibrations known as oil-whirl and oil-whip phenomena. A significant influence on the occurrence of oil-whip phenomena is attributed to the bearing stiffness and damping, which depend both on the kinematic state of the supporting elements and the thermal condition as well as the occurrence of outgassing processes. For modelling the bearing behaviour, the Reynolds equation with mass-conserving cavitation regarding the two-phase model and the 3D energy as well as heat conduction equation is solved. To evaluate the impact of cavitation, run-up simulations are carried out assuming a fully (Half-Sommerfeld) or partially filled lubrication gap. The resulting rotor responses are compared with the shaft motion measurement. Also, the normalized eccentricity, the minimum lubricant fraction and the thermal bearing condition are discussed.

Nonlinear Analysis of Rotor-Stator-Bearing System Unsteady Oil Film Force

2013 ◽  
Vol 341-342 ◽  
pp. 395-399
Author(s):  
Gui Zhen Liu ◽  
Ying Yu ◽  
Bang Chun Wen
Keyword(s):  
Dynamics Model ◽  
Oil Film ◽  
Oil Whip ◽  
Film Instability ◽  
Oil Whirl ◽  
Amplitude Spectra ◽  
Axis Orbit ◽  
Speed Change ◽  
Effective Diagnosis ◽  
Bearing System

According to the LaGrange energy equation, the establishment of the unsteady oil film force of the rotor - stator - bearing system dynamics model, the application of numerical method, the system with the speed change time domain waveforms, amplitude spectra and Axis Orbit, the results show that: the unsteady oil film force and speed of change is closely related to changes in the process of oil film force oil whirl Oil Whip. Provide a theoretical basis for effective diagnosis of rotor - stator - bearing oil film instability fault research.

Vibration Analysis of Statically Indeterminate Rotors With Hydrodynamic Bearings

1998 ◽  
Vol 120 (4) ◽  
pp. 781-788 ◽  
Author(s):  
N. S. Feng ◽  
E. J. Hahn
Keyword(s):  
Vibration Analysis ◽  
Operating Conditions ◽  
System Stability ◽  
Hydrodynamic Bearings ◽  
Hydrodynamic Bearing ◽  
Unbalance Response ◽  
Tilting Pad ◽  
The Stability ◽  
Rotor Bearings ◽  
Stiffness And Damping

In statically indeterminate rotor bearings systems, where the rotor is supported by one or more hydrodynamic bearings, the reactions at each hydrodynamic bearing, and hence its stiffness and damping properties depend not only on the bearing type, the operating conditions and the bearing dimensions but also on the relative lateral alignment between the journal and the bearing housing; the alignment, therefore, has a significant influence on the system stability and unbalance response. Additional complications arise if nonsymmetric bearing types such as elliptic or tilting pad bearings are present. An iterative procedure is outlined which enables the bearing reactions to be determined at any speed, thereby enabling even large systems such as turbomachinery to be rapidly analyzed in conjunction with existing linear rotor bearing vibration analysis software. Sample numerical examples show how misalignment and bearing type can affect the natural frequencies, the stability threshold, and the unbalance response of such statically indeterminate systems.

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